1. Field of the Invention
This invention relates primarily to valves which control the mix of hot and cold water. More particularly, the invention relates to valves of the foregoing type wherein the mixture of hot and cold water has pressure-compensation capability.
2. Description of the Art
It is known in the art to provide pressure-compensated valves having separate upper and lower housings, a separate water pressure-balancing cartridge, and a rotatable disk for sliding over spring loaded water inlet seals. With such valves, it becomes necessary sometimes to replace wearable inlet seals. In most instances, these are located inside a pressure-balancing cartridge. For example, see elements 71 and 72 in U.S. Pat. No. 3,921,659 and 75-78 in U.S. Pat. No. 4,095,610. Thus when replacement is required, it is necessary to either discard the entire cartridge or attempt to remove the worn seals and replace them.
One particularly troubling problem with respect to pressure-compensated valves relates to the reciprocating pistons which act in conjunction with a pressure-activated diaphragm. These pistons are designed to reciprocate in close fitting bores. This arrangement necessitates very tight bore alignment and positioning of the pistons in a perpendicular manner with respect to the bore in order to prevent the pistons from binding. For efficient operation, the pistons must be free to move in a reciprocating manner in response to pressure differences in order to effect a near constant mix ratio of water in the inlet passages. Diaphragm activated pistons of the foregoing type are shown in U.S. Pat. Nos. 3,724,480; 3,921,659; and 4,095,610. This requires the use of unduly expensive manufacturing processes and/or extensive quality control to avoid problems due to tolerance differences. It is also desired to simplify the procedures and costs to assemble such valves.
Thus, it can be seen that a need exists for an improved pressure-compensated mixing valve.